We believe that 100% of our members should be sponsored by their employers!  Consider asking your employer to support your high performance development.  Here is a sample letter that may be just the key. If the wording doesn't exactly suit your style or situation, just use what what you feel will be effective. Good luck!

Subject: My Professional Development in 2009 -- Professional Organization Membership Dues

I am actively involved in a professional organization, the American Society For Training and Development, Northeast Florida chapter.  My membership in this organization gives me access to tools, solutions, and insights that I implement daily in my job.  Each month this organization holds one or more professional development workshops, at which local and national speakers address the membership on general leadership/professional development topics or developments specifically of interest to the training industry.  These meetings always provide me with some sort of take-away that I can apply to my current position or project. 

These workshops also provide great networking opportunities.  Because of my membership I have access to contacts in every industry and of every skill set.  On a monthly basis I can reach out to these folks for guidance, tips and some amazing practical advice on projects I am working on here at XYZ Company.

Finally, my serving as a board member/committee member/volunteer for ASTD is giving me additional opportunities to develop my leadership and communication skills. 
 
My membership in this organization positively impacts my performance here at XYZ Company.   I would like to request that my membership fees are considered as part of my professional development and are supported by the company. Ideally, I will be a member of both the Local and National organizations. The fees for 2009 are $419.00 (less than the cost of a single out-of-town seminar) and include full membership benefits and a whole year's worth of professional development workshops.

Sincerely,
Your Name